Interferometric measurement of non-homogeneous multi-material surfaces

Abstract

Correction factors for the ALR and PTR parameters of magnetic-head sliders are determined by calculating an effective reflectivity and a corresponding PCOR at each pixel of the air-bearing surface. The absolute value of reflectivity at each pixel of the AlTiC air-bearing surface is obtained from an empirical equation relating it to modulation. The ratio of Al 2 O 3 and TiC in the AlTiC surface is then calculated at every pixel assuming a linear relationship between the absolute value of AlTiC reflectivity and the theoretical reflectivity of each constituent. The linear relationship is then also used to calculate the effective (complex) reflectivity for the AlTiC material from the relative concentrations of Al 2 O 3 and TiC at each pixel.

The invention claimed is: 
     
       1. A method of calibrating an interferometric profilometer used for measuring a pole-tip recession in a magnetic-head slider having an air-bearing surface made of a composite material, the method comprising the following steps:
 using said profilometer to measure interference signals produced at a plurality of pixels by a first test material and by a second test material; 
 assuming that M ij   exp =α|r th |−β represents an empirical relationship between a known value of reflectivity r th  for a material and an experimental modulation M ij   exp  produced by the material when measured with said profilometer, where α and β are system-dependent parameters related to the profilometer; and 
 calculating α and β using said empirical relationship expressed as
     M   1   exp   =α|r   1   th |−β,
 
     M   2   exp   =αr   2   th |−β,
 
 
 where r 1   th  and r 2   th  are theoretical values of reflectivity of said first test material and second test material, respectively, and M 1   exp  and M 2   exp  are experimental modulations produced by said first test material and second test material, respectively, when measured with the profilometer; said calculating step being carried out with a computer; 
 thereby calibrating the profilometer for measuring the pole-tip recession in the magnetic-head slider. 
 
     
     
       2. The method of  claim 1 , wherein said first test material is a pole tip region and said second test material is a trailing edge surface of the magnetic-head slider. 
     
     
       3. A method of calibrating an interferometric profilometer used for measuring a trailing-edge recession in a magnetic-head slider having an air-bearing surface made of a composite material, the method comprising the following steps:
 using said profilometer to measure interference signals produced at a plurality of pixels by a first test material and by a second test material; 
 assuming that M ij   exp =α|r th |−β represents an empirical relationship between a known value of reflectivity r th  for a material and an experimental modulation M ij   exp  produced by the material when measured with said profilometer, where α and β are system-dependent parameters related to the profilometer; and 
 calculating α and β using said empirical relationship expressed as
     M   1   exp   =α|r   1   th |−β,
 
     M   2   exp   =αr   2   th |−β,
 
 
 where r 1   th  and r 2   th  are theoretical values of reflectivity of said first test material and second test material, respectively, and M 1   exp  and M 2   exp  are experimental modulations produced by said first test material and second test material, respectively, when measured with the profilometer; said calculating step being carried out with a computer; 
 thereby calibrating the profilometer for measuring the trailing-edge recession in the magnetic-head slider. 
 
     
     
       4. The method of  claim 3 , wherein said first test material is a pole tip region and said second test material is a trailing edge surface of the magnetic-head slider.